ELECTRON MICROSCOPIC EVIDENCE FOR THE LOCATION AND AMOUNT OF ION ACCUMULATION BY SPINACH CHLOROPLASTS

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Abstract
Electron-opaque particles occur on the lamellae of spinach chloroplasts under conditions favoring the uptake of certain bivalent cations. These particles are apparently amorphous deposits which increase in size during illumination. The mean diameter is largest with strontium (20.6 m[mu] for a 15 min illumination), intermediate with calcium, and smallest with barium. The frequency is about 100 deposits per [mu]2 of lamellae. The electron-opaque particles are located on the inner surface of the thylakoid, stressing the difference between the two sides f the membrane.